Looking for some help with voltages

Can anyone give me an idea of the max CPU & QPI/DRAM voltage I can use with an i7 975 Extreme Bloomfield edition with water cooling (chilled)? I'm trying to get a stable 4.5Ghz, I can get 4.4 stable, but anything over that seems impossible at the moment. Thanks!!

System:
Intel i7 975 Extreme Bloomfield @ 3.33Ghz
Rampage II Extreme motherboard
6gb Corsair Dominator 1600 DDR3 8-8-8-24
ATI Radeon 4870 video card
Crucial 64gb SSD for running the OS & other core applications
4 other SATA HDs for everything else
Corsair 1000w PSU
Custom dual rad water cooling loop (CPU only)